The present invention relates to a sintered body of cemented carbide with varying contents of binder phase and a method of making the same.
In order to obtain good properties in cemented carbide, it is often desirable to have a tough core (with a high content of binder phase) surrounded by a more wear resistant cover (having a low content of binder phase).
One method of attaining this effect is to make a sintered body with a tough and less wear resistant carbide grade in the center surrounded by a more wear resistant and less tough grade. During sintering however, carbide diffusion of the binder phase usually takes place which in many cases leads to the sintered body having an almost uniform binder phase cement.
A varying content of binder phase in a sintered body of cemented carbide can be obtained, however, by means of the so called compound hard metal technique. This technique uses cemented carbide powder with different grain sizes (for example, according to European patent EP No. 111 600) or has the cemented carbide body divided in zones with different grain sizes (for example, according to GB-A No. 806 406) by which it has generally been possible to obtain a certain difference of binder pure content between different parts of the cemented carbide body. In these cases, however, no difference in wear resistance between the different parts is obtained because the fine grained part will have a greater binder phase content than the more coarse grained part.